Fluidic timer

ABSTRACT

An arrangement for producing a fluid output signal of a specified duration, for use in fluidic logic and control circuits, comprising a liquid fill tank, a fill circuit which upon initiation of the circuit function is arranged to direct a predetermined volume of liquid into the tank by a continued activation of the circuit until the liquid in the tank reaches a specified level and a tank emptying and signal output circuit which removes liquid from the tank and produces the output signals as long as the level of liquid in the tank is above a second lower level, by means of a sensing tube having its outlet located at the second level which controls a pair of jet amplifiers so as to produce the output signal whenever the sensing tube is aspirating liquid from the tank and discontinue the output signal when the tube begins to aspirate air. The rate of aspiration of the sensing tube liquid and the volume of fluid supplied by the fill circuit controls the duration of the output signal.

United States Patent 1 Barnard 1 Jan. 30, 1973 [54] FLUIDIC TIMER [75]Inventor: Daniel 15; Barnard, Birmingham,

Mich.

[731 Assignee: The Bendi t Corporation [22] Filed: Dec. 21, 1970 [21]Appl. No.: 99,801

[52] U.S. C1 ..137/81.5 [51] 1nt.Cl. ..Fl5c 1/12 [58] Field of Search..137/8l.5

[56] References Cited UNITED STATES PATENTS 3,331,380 7/1967 Schonfeldet al ..1 37/815 3,498,307 3/1970 Adams ..137/81.5 3,545,468 12/1970Freeman et al ..137/8 1 .5 3,547,414 12/1970 Nardi ..137/81.5 3,581,7546/1971 Adams ..137/81.5 3,603,336 9/1971 Fichter et al. ..l37/8l.5

Primary ExaminerSamuel Scott Attorney-John R. Benefiel and Plante,Hartz, Smith & Thompson [57] ABSTRACT An arrangement for producing afluid output signal of a specified duration, for use in fluidic logicand control circuits, comprising a liquid fill tank, a fill circuitwhich upon initiation of the circuit function is arranged to direct apredetermined volume of liquid into the tank by a continued activationof the circuit until the liquid in the tank reaches a specified leveland a tank emptying and signal output circuit which removes liquid fromthe tank and produces the output signals as long as the level of liquidin the tank is above a second lower level, by means of a sensing tubehaving its outlet located at the second level which controls a pair ofjet amplifiers so as to produce the output signal whenever the sensingtube is aspirating liquid from the tank and discontinue the outputsignal when the tube begins to aspirate air. The rate of aspiration ofthe sensing tube liquid and the volume of fluid supplied by the fillcircuit controls the duration of the output signal.

11 Claims, 2 Drawing Figures 07/2 (249 T/ON Dev/c: Z

PATENTEDJANSO I975 3.713.456

rz- IHIHHIIIIII INVENTOR DANIEL D. BARNARD WNW FLUIDIC TIMER BACKGROUNDOF THE INVENTION 1. Field of the Invention This invention concernsfluidics and more specifically fluidic timers for use in fluidic logicand control circuits.

2. Description of the Prior Art Fluidic circuits in many applicationsrequire time delays or holds of relatively long duration ranging fromseveral seconds to several minutes. Prior art devices rely for the mostpart on circuits which count periodic events such as the output of anoscillator, but for these longer time intervals the counting circuitsbecome unduly complex and expensive unless very long period oscillatorsare used. Such low frequency oscillations are difficult to achieve andoften are inaccurate and unreliable.

Therefore, it is an object of the present invention to provide a fluidictimer capable of producing accurately timed signals of relatively longduration without the need for complex and expensive counting circuits,and which uses a fixed minimal number of fluid amplifiers regardless ofthe length of the time delay.

SUMMARY OF THE INVENTION This object and others which will becomeapparent upon a reading of the following specification and claims isaccomplished by providing a liquid fill tank, a fill circuit which uponinitiation of the circuit function directs a predetermined volume ofliquid into the tank by continued activation of the circuit until theliquid in the tank reaches a specified level, and a tank emptying andsignal output circuit which removes liquid from the tank and producesthe output timing signal as long as the level of liquid in the tank isabove a second lower level, with these functions accomplished by meansof a sensing tube having its outlet located at the second level, andwhich controls a pair of jet amplifiers so as to produce the outputsignal whenever the sensing tube is aspirating liquid from the tank andto discontinue the signal upon aspirating air.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic representationof one embodiment of the fluidic timer circuit of the present invention.

FIG. 2 is a schematic representation of a second embodiment of thefluidic timer circuit according to the present invention.

DESCRIPTION OF THE EMBODIMENT In the following detailed description,certain specific terminology will be used for the sake of clarity andspecific embodiments described in order to provide a full and completeunderstanding of the invention, but it is to be understood that theinvention is not so limited and may be practiced in a variety of formsand embodiments.

Referring to the drawing and particularly FIG. 1, the fluidic timercircuit is represented, comprised of four major components: a bistablejet amplifier 12, a liquid till tank 14, a fill control circuit 16, atank emptying and signal output circuit 18.

The bistable jet amplifier 12 per se is well known in the art andconsists of a power jet channel 20 which directs fluid received from asource 22 entirely into either output leg 24 or 26, depending on thehistory of control signals received in control passages 28 and 30, dueto the tendency of the power jet to attach to either wall 32 or 34.

One of the control signal ports 28 is connected via passage 36 to thefill control circuit 16 while the other port 30 is connected via passage38 to a source of an initiating signal 40 such as another portion of thelogic circuit, which as indicated may transmit a pressure pulse of asquare wave form 42 to set the power stream into the outlet leg 24.

Outlet leg 26 directs the fluid to the sump or return 44 via passage 46while output leg 24 directs the liquid into the liquid fill tank 14 viapassage 48.

The volume of liquid directed into the liquid fill tank 14 via outlet 24is controlled by the fill control circuit 16 which basically functionsas a level sensing arrangement. A sensing tube 50 having an outlet 52positioned at level A in the liquid fill tank 14 is connected to acontrol port 54 of a jet amplifier 56, which includes a power streamchannel 58 directing a power jet from source 60 toward outlet legs 62and 64. A second control port 66 opposite control port 54 is providedand vented so that aspiration of air will preclude any significant wallattachment effect with surface 65 tending to pull the power jet towardoutlet leg 62 since the formation of the low pressure region necessarytherefor is prevented.

Similarly, whenever the liquid level is less than level A, sensing tube50 aspirates air, which destroys any wall attachment effect of the powerjet with surface 67, so that under these conditions flow will be carriedroughly equally by outlet legs 62 and 64. However, whenever the liquidlevel reaches level A, the sensing tube 50 is blocked from aspiratingair, allowing a low pressure region and resulting wall attachment effectwith surface 67 to occur, thus directing the power jet substantiallyentirely from outlet leg 64.

Outlet legs 62 and 64 in turn are connected to the control ports 68 and70 of another, monostable, jet amplifier 72 which includes a powerstream passage 74 directing a power jet from source 76 toward outletlegs 78 and 80. A wall attachment surface depicted schematically at 82is positioned just upstream of outlet leg 78 so that flow from the powerjet is monostable with respect to outlet leg 78 and hence tends to exitentirely through leg 78, while flow through outlet leg is astable andwill continue only so long as a control signal at port 70 is strongenough to overcome the wall attachment effect.

Outlet leg 80 is connected to passage 36 connected to control port 28 ofthe bistable jet amplifier 12 while outlet leg 78 is connected to thesump or return 44.

Positioned at level B in the liquid fill tank 14 is the outlet 84 of asecond sensing tube 86 operatively connected to the tank emptying andsignal output circuit 18.

The circuit 18 includes a first jet amplifier 88 having a power streampassage 90 directing a power jet from source 92 toward outlet legs. 94and 96.

A control port 98 is provided connected to sensing tube 86.

A second control port 100 is provided opposite control port 98 andvented so that air is aspirated precluding any wall attachment effectwith surface 99 in the same manner as in circuit 16 so that flow tendsto exit entirely through outlet leg 96.

Similarly, whenever the liquid level in fill tank 14 declines belowlevel B, the sensing tube 86 will aspirate air, which will in turn tendto destroy the wall attachment effect of the power jet and surface 101so that flow will exit roughly equally from outlet legs 94 and 96.However, whenever the liquid level reaches level B the sensing tube 86will be blocked from aspirating air, and will begin to aspirate liquid,allowing a low pressure region to form and produce wall attachment withoutlet leg 96.

Outlet legs 94 and 96 are connected via passages 102, 104 with controlports 106 and 108 of a second, monostable, jet amplifier 110, which alsoincludes a power stream passage 112 directing a power jet from source114 toward output legs 116 and 118.

A wall attachment surface depicted schematically at 120 is provided justupstream from outlet leg 118 and positioned so that the power jet tendsto attach thereto and exit entirely from outlet leg 118.

Outlet legs 116 and 118 are connected to output passages 120, 122 inturn connected to utilization devices on circuits depicted in block format 124 and 126.

OPERATION Assuming the level of liquid in fill tank 14 to be just belowlevel B, and the condition of bistable amplifier 12 to be that with thepower jet directed entirely through outlet leg 26 to the sump 44, thesensing tube 86 will be continuously aspirating air.

This causes the power jet of the jet amplifier 88 to split equally intooutlet legs 94, 96. Since the flow at the control ports 106 and 108 isthus equal, their effect on the power jet of monostable jet amplifier110 is nil, and hence due to attachment to wall 120, the power jet willexit entirely from outlet leg 118, thus providing an output 12 at theoutput passage 122.

To initiate the timed interval, a control pulse 42 is directed tocontrol port 30 via passage 38, which causes the power jet of bistablejet amplifier 12 to shift to its other stable condition with flowexiting entirely from passage 24, so that liquid is directed into thefill tank 14 via passage 48. As soon as the liquid level reaches B,sensing tube 86 begins to aspirate liquid, allowing the amplifier 88 tofunction so as to direct flow entirely from outlet 96, in turn causing acontrol signal to be applied at control port 108 of monostable jetamplifier 110. This causes a switching of the power jet to outlet leg116, with resultant initiation of the signal t in passage 120 definingthe beginning of the timed interval.

The output of the bistable jet amplifier 12 is selected to be greaterthan the aspiration rate of sensing tube 86 so that there is a net flowinto the fill tank 14.

As soon as the level in the till tank 14 reaches level A, sensing tube50 begins to aspirate the liquid into port 54, causing the jet amplifier56 to function so as to allow wall attachment of the power jet andsurface 66 so that flow exits entirely from outlet leg 64, applying acontrol signal solely at port 70, which causes switching of the powerjet of monostable amplifier 72 from outlet leg 78 to outlet leg 80. Theresulting control signal in passage 36 introduced a port 28 of thebistable jet amplifier 12 then switches the power jet of bistable jetamplifier 12 to its original bistable condition with flow exitingentirely from outlet leg 26 to the sump 44 discontinuing further flowinto the fill tank 14.

Sensing tube 86 continues to aspirate liquid so signal t, remainsuninterrupted until the liquid level is again reduced to level B, atwhich point aspiration of air into sensing tube 86 causes switching ofmonostable jet amplifier back to its original state, hence discontinuingsignal t and restarting signal I It can be appreciated that the timeinterval during which the signal t is present is controlled by thevolume of liquid introduced by the bistable jet amplifier 12 ascontrolled by the fill control circuit 16 as well as the aspiration ratethrough sensing tube 86, and hence the period may be controlled overwide limits without the necessity of additional complex counting orother circuits.

As depicted in FIG. 2, the fluid timer circuit may be rendered periodicby providing a feedback passage 128 connecting passages 122 and 38instead of an input from the rest of the logic circuitry 40.

Signal 1 will then function as the initiating signal 42, causing acyclical switching from t to t, and back of a predetermining frequency.

Many variations of this system are, of course, possible within the scopeof the present invention.

For example, this circuit while particularly suited to liquid poweredsystems could be adapted to pneumatic logic packages as a separate loophaving its own power supply and interface to the pneumatic logic withsimple infinite impedance devices.

In addition numerous alternate methods of creating the monostablecharacteristics of the various amplifiers are possible, such asproviding bias ports, varying the geometry of the control ports, etc.,as is well known in the art. Similarly, other level sensing and controlcircuits could be provided.

From the above description, it can be appreciated that a fluidic timingarrangement has been provided which is capable of providing accuratelytimed intervals of relatively long duration without the need forexpensive and complex circuitry.

What is claimed is:

1. A fluidic timer comprising:

tank means for receiving a volume of liquid;

fill means for introducing a volume of liquid into said tank meansincluding means for sensing the level of liquid in said tank means;

emptying means for removing said volume of liquid from said tank meansat a predetermined rate; signal means producing a signal correspondingto the time elapsed during removal of said volume of liquid from saidtank means, whereby a signal corresponding to an interval the length ofwhich is determined by the volume of said liquid introduced and the rateof removal is provided.

2. The timer of claim 1 wherein said emptying means includes a sensingtube extending into said tank means having an outlet at a predeterminedlevel in said tank means and further includes a first emptying means jetamplifier having a control port and means connecting said control portwith said sensing tube to cause liquid to be aspirated from said tankmeans through said sensor tube and wherein said first emptying means jetamplifier has a pair of outlets and tends to direct flow en-- tirelythrough one of said outlets whenever said sensing tube is aspiratingliquid, and wherein said signal means includes a second monostable jetamplifier and further includes means connecting opposing control portsof said jet amplifier with said pair of outlets.

3. The timer of claim 1 wherein said level sensing means includes asensing tube having an outlet located at a level in said tank means, andalso includes means for discontinuing the introduction of liquid intosaid tank when the liquid level in said tank reaches said sensing tubeoutlet.

4. The timer of claim 3 wherein said fill means includes a bistable jetamplifier and further includes means for directing one output of saidbistable jet amplifier into said tank means and further includes meansfor switching the bistable jet amplifier from said one output when saidliquid level in said tank reaches said sensing tube level.

5. The timer of claim 4 wherein said switching means includes a firstjet amplifier having a control port connected to said sensing tube.

6. The timer of claim 5 wherein said switching means further includes asecond, monostable jet amplifier, means connecting two outlets of saidfirst jet amplifier to two opposing control ports of said secondmonostable jet amplifier, and means connecting the astable outlet ofsaid second monostable jet amplifier to a control port of said bistablejet amplifier directed to switch said bistable jet amplifier from saidone output.

7. The timer of claim 1 wherein said emptying means includes a sensingtube extending into said tank means having an outlet at a predeterminedlevel in said tank means and further includes means for drawing liquidout of said tank means through said sensing tube.

8. The timer of claim 7 wherein said level sensing means includes asecond sensing tube having an outlet located at a level in said tankmeans above said predetermined level, and also includes means fordiscontinuing the introduction of liquid into said tank when the liquidlevel in said tank reaches said second sensing tube outlet.

9. The timer of claim 8 wherein said fill means includes a bistable jetamplifier having a pair of outputs and further includes means fordirecting one output of said bistable jet amplifier into said tank meansand further includes means for switching the bistable jet amplifier fromsaid one output to the other output when said liquid level in said tankreaches said second sensing tube level.

10. The timer of claim 9 wherein said switching means includes a firstjet amplifier having a control port connected to said second sensingtube.

11. The timer of claim 10 wherein said switching means further includesa monostable jet amplifier, means connecting two outlets of said firstjet amplifier to two opposing control ports of said monostable jetamplifier, and means connecting the astable outlet of said monostablejet amplifier to a control port of said bistable jet amplifier directedto switch said bistable jet amplifier from said one output.

1. A fluidic timer comprising: tank means for receiving a volume ofliquid; fill means for introducing a volume of liquid into said tankmeans including means for sensing the level of liquid in said tankmeans; emptying means for removing said volume of liquid from said tankmeans at a predetermined rate; signal means producing a signalcorresponding to the time elapsed during removal of said volume ofliquid from said tank means, whereby a signal corresponding to aninterval the length of which is determined by the volume of said liquidintroduced and the rate of removal is provided.
 1. A fluidic timercomprising: tank means for receiving a volume of liquid; fill means forintroducing a volume of liquid into said tank means including means forsensing the level of liquid in said tank means; emptying means forremoving said volume of liquid from said tank means at a predeterminedrate; signal means producing a signal corresponding to the time elapsedduring removal of said volume of liquid from said tank means, whereby asignal corresponding to an interval the length of which is determined bythe volume of said liquid introduced and the rate of removal isprovided.
 2. The timer of claim 1 wherein said emptying means includes asensing tube extending into said tank means having an outlet at apredetermined level in said tank means and further includes a firstemptying means jet amplifier having a control port and means connectingsaid control port with said sensing tube to cause liquid to be aspiratedfrom said tank means through said sensor tube and wherein said firstemptying means jet amplifier has a pair of outlets and tends to directflow entirely through one of said outlets whenever said sensing tube isaspirating liquid, and wherein said signal means includes a secondmonostable jet amplifier and further includes means connecting opposingcontrol ports of said jet amplifier with said pair of outlets.
 3. Thetimer of claim 1 wherein said level sensing means includes a sensingtube having an outlet located at a level in said tank means, and alsoincludes means for discontinuing the introduction of liquid into saidtank when the liquid level in said tank reaches said sensing tubeoutlet.
 4. The timer of claim 3 wherein said fill means includes abistable jet amplifier and further includes means for directing oneoutput of said bistable jet amplifier into said tank means and furtherincludes means for switching the bistable jet amplifier from said oneoutput when said liquid level in said tank reaches said sensing tubelevel.
 5. The timer of claim 4 wherein said switching means includes afirst jet amplifier having a control port connected to said sensingtube.
 6. The timer of claim 5 wherein said switching means furtherincludes a second, monostable jet amplifier, means connecting twooutlets of said first jet amplifier to two opposing control ports ofsaid second monostable jet amplifier, and means connecting the astableoutlet of said second monostable jet ampLifier to a control port of saidbistable jet amplifier directed to switch said bistable jet amplifierfrom said one output.
 7. The timer of claim 1 wherein said emptyingmeans includes a sensing tube extending into said tank means having anoutlet at a predetermined level in said tank means and further includesmeans for drawing liquid out of said tank means through said sensingtube.
 8. The timer of claim 7 wherein said level sensing means includesa second sensing tube having an outlet located at a level in said tankmeans above said predetermined level, and also includes means fordiscontinuing the introduction of liquid into said tank when the liquidlevel in said tank reaches said second sensing tube outlet.
 9. The timerof claim 8 wherein said fill means includes a bistable jet amplifierhaving a pair of outputs and further includes means for directing oneoutput of said bistable jet amplifier into said tank means and furtherincludes means for switching the bistable jet amplifier from said oneoutput to the other output when said liquid level in said tank reachessaid second sensing tube level.
 10. The timer of claim 9 wherein saidswitching means includes a first jet amplifier having a control portconnected to said second sensing tube.